Avoid entry point lookups in Node/Group metaclasses

[danielhollas]

It turns out a big part of why aiida.orm import is so slow are costly entry point lookups
in AbstractNodeMeta and GroupMeta metaclasses.

Commit 1: _plugin_type_string and _query_type_string

These class attributes require a look up whether the Node class has a
registered entry point which can have a non-negligible cost. These
attributes were defined in the AbstractNodeMeta class, which is the
metaclass of the Node class, which would cause this code to be
executed as soon as the class was imported.

Here, the AbstractNodeMeta metaclass is removed. The
_plugin_type_string and _query_type_string class attributes are
changed to class properties. The actual value is stored in the private
attribute analog which is defined lazily the first time the property is
accessed.

Commit 2: __type_string

This attribute was defined in the GroupMeta metaclass.
Because this was the only purpose of this metaclass,
we can fully remove it and use the same strategy as above.

Commit 3: Avoiding aiida.cmdline import

There are some further entry point lookups in metaclasses defined in aiida.cmdline used for the click interface.
It's not that clear how to get rid of those, but here we at least avoid importing aiida.cmdline from aiida.orm and aiida.manage,
which also speeds up import aiida.

With this last change, there are no entry point lookups during aiida.orm import. 🎉

Benchmarks

TODO: I will add benchmarks shortly...

[danielhollas]

Benchmarks against the current main branch

import aiida

$ hyperfine -w 2 "PYTHONPATH=/home/hollas/atmospec/aiida-core-main python -c 'import aiida'" "python -c 'import aiida'"
Benchmark 1: PYTHONPATH=/home/hollas/atmospec/aiida-core-main python -c 'import aiida'
  Time (mean ± σ):     287.6 ms ±  23.5 ms    [User: 257.4 ms, System: 29.5 ms]
  Range (min … max):   262.2 ms … 317.5 ms    10 runs
 
Benchmark 2: python -c 'import aiida'
  Time (mean ± σ):     239.6 ms ±   9.8 ms    [User: 213.5 ms, System: 25.5 ms]
  Range (min … max):   223.5 ms … 254.1 ms    12 runs
 
Summary
  'python -c 'import aiida'' ran
    1.20 ± 0.11 times faster than 'PYTHONPATH=/home/hollas/atmospec/aiida-core-main python -c 'import aiida''

import aiida.orm

$ hyperfine -w 2 "PYTHONPATH=/home/hollas/atmospec/aiida-core-main python -c 'import aiida.orm'" "python -c 'import aiida.orm'"
Benchmark 1: PYTHONPATH=/home/hollas/atmospec/aiida-core-main python -c 'import aiida.orm'
  Time (mean ± σ):     997.2 ms ± 199.5 ms    [User: 1530.3 ms, System: 711.7 ms]
  Range (min … max):   735.8 ms … 1360.8 ms    10 runs
 
Benchmark 2: python -c 'import aiida.orm'
  Time (mean ± σ):     503.3 ms ±   9.8 ms    [User: 1029.0 ms, System: 717.3 ms]
  Range (min … max):   491.5 ms … 522.9 ms    10 runs
 
Summary
  'python -c 'import aiida.orm'' ran
    1.98 ± 0.40 times faster than 'PYTHONPATH=/home/hollas/atmospec/aiida-core-main python -c 'import aiida.orm''

[danielhollas]

The one failing Rabbitmq test is confusing. It only happened for RMQ version 3.7, but it happened twice already so I am not sure if it is just a flaky test or not.

[danielhollas]

@sphuber @unkcpz could you take a look? (I cannot assign reviewers on this repo apparently)

[sphuber]

There were two more top-level imports of aiida.cmdline in aiida.orm that I also removed. I was a bit hesitant to merge this, since it is potentially a significant change and could break things without us noticing. But let's merge. If there is a problem, hopefully we will find it before release by running of the main branch.

[sphuber]

Thanks @danielhollas

[danielhollas]

Thanks @sphuber! I'll work on submitting the other PRs which should be less risky than this one.